Service providers delivering video services typically will include redundant links from a video server to the head end routing switch platforms so that delivery of video trough the communications network to the end user/video subscribers is ensured in the event of a failure in one of the links. In order for redundant links to work, some mechanism must be capable of detecting a condition corresponding to failure along the link providing service. Typically detection is accompanied with an alarm which is sent back to a network management system which makes appropriate changes to the system to ensure routing and forwarding of the video transmissions to their intended recipient subscribers.
Referring now to FIG. 1, known redundant delivery of video services in an ATM network 400 is described. A video server 100 is coupled to a first and a second routing switch platform 140, 142 over a first ATM link 110 and a second ATM link 120 respectively. The first routing switch platform 140 acts as a root node for a first point to multipoint (P2MP) ATM connection 150 for delivering video to a number of video subscribers 90 while the second routing switch platform acts as a root node for a second P2MP ATM connection 152. A network management system (NMS) 200 monitors and administrates the first and second routing switch platforms 140 and 142 via a first control link 210 and a second control link 220 respectively. Typically this NMS 200 understands how to manage multi-endpoint paths (MEPs) such as the P2MP connections 150, 152. Each routing switch platform 140, 142 has an ATM input interface acting as the single root point in the respective point to multi-point connection. The first routing switch platform 140 has a first ATM input interface 141 for the first P2MP connection 150, and the second routing switch platform 142 has a second ATM input interface 143 for the second P2MP connection 152.
The P2MP video signals propagate through the remaining network 400 to leaf node DSLAMs (digital subscriber line access multiplexers) 301, 302, 303 which finally are coupled to and deliver the video service to video subscribers 90 (VSs). Two leaf node DSLAMs 301, 302 are coupled to one video subscriber 90 each, while one leaf node DSLAM 303 is coupled to three video subscribers 90. In the system shown in FIG. 1, typically each virtual channel over ATM identified by a VPI/VCI (virtual path identifier/virtual channel identifier) corresponds to a single TV channel.
In known systems, video streams may or may not be delivered at the same time over both of the ATM links 110, 120. In some cases video would be delivered only over the second ATM link 120 which is referred to as the working link. The second routing switch platform 142 is referred to as the working node, while the first routing switch platform 140 is referred to as the protection node. The protection node 140 acts as a backup for the working node 142, and is coupled to the video server 100 by the first ATM link 110 which is referred to as the protection link 110.
In the case of a failure 105 along for example the second ATM link 120 (indicated by an X in FIG. 1), the second routing switch platform 142 will send an alarm to the NMS 200 that the second ARM input interface 143 has failed, and the NMS 200 will understand that the second routing switch platform 142 can no longer act as the root node, and will assign a new root node to ensure delivery of service to the leaf node DSLAMs 301, 302, 303. In FIG. 1, the new root node would be the first routing switch platform 140 which before the failure was the protection node. In the case that video was previously delivered only over one link, namely wording ATM link 105, and if the NMS 200 has management capacity over the video server 100, the assignment of the first routing switch platform 140 as the new root node is accompanied by the NMS sending a directive to the video server 100 to transmit video to the first routing switch platform 140. In the case that video was being sent to both redundant nodes 140, 142, the assignment of the first routing switch platform 140 as the new root node causes video already arriving at the first routing switch platform to commence being broadcast therefrom.
To provide IPTV/Triple play services to its video subscribers, service providers are moving towards use of GigE/IP network infrastructure, especially at the video server end including the root or head end nodes of the network while keeping in the interim a large portion of the communications network 400 ATM infrastructure based. This is especially the case where P2MP connections are present since it is very difficult and costly to develop and implement a new VLAN based P2MP connection scheme. Keeping the ATM P2MP connections while improving delivery to the root nodes with GigE/IP would be less costly. Configuring monitoring, redundancy, and coordinating alarms become important issues to be resolved especially at points in the network where these two infrastructures (ATM and GigE/IP) are being integrated.